Typically during neurological procedures, stereotactic guidance is employed by a physician to reach a target site. Stereotactic guidance is generally defined as the ability to locate and access on object in a three-dimensional space. Further, surgical delivery by an instrument is often guided by use of three-dimensional scanning technique such as computed tomography (CT) or magnetic resonance imaging (MRI). Typically, such stereotactic procedures require the use of a stereotactic head frame, which is generally referred to as a frame-based stereotaxy procedure. A typical stereotactic head frame is a halo-like or ring-like device that is rigidly affixed to the patient's skull by means of pins or screws. A semi-circular arc for holding an instrument is attached to the head frame.
When the head frame is fixed or secured, the head frame is used to define a target and a trajectory to the target. This can be achieved, for example, with use of CT or MRI images. The head frame may also be used as a guide for delivering various types of instruments, such as a biopsy needle or DBS (Deep Brain Stimulation) leads or electrodes.
In order to correct positioning and adjustment of the head frame and the semi-circular arc, the head frame and arc typically include graduations or indentations that are scaled to provide separate discreet movements along the scale of the head frame and arc. This requires knowledge and long experience by the user. The target and trajectory adjustments and positioning is manually adjusted via adjustment knobs arranged on the head frame and these manual adjustments of the various scales to adjust the x, y, and z coordinates, as well as the rotations about these coordinates for targeting and trajectory are susceptible for human error and are time consuming. Particularly, the steps of attaching the arc to the support members of the head frame and adjusting the x coordinate after attachment of the arc to the head frame via the support members are difficult and cumbersome and also require experience and are therefore time consuming and susceptible for human error.
It is therefore a need to provide a stereotactic surgical instrument where the mounting or attachment of the arc to the head frame is facilitated and also in a manner that is accurate and precise in line with the high demands on tolerance and precision in such an environment.